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Can you have too much vitamin D?
The simple answer is yes. The principle that it’s possible to get too much of a good thing even extends to cancer-fighting, heart-protective vitamin D. You can take too much of just about any vitamin or supplement, and it is possible to suffer vitamin D toxicity.
How much is enough vitamin D? The National Institutes of Health (NIH) ‘s Office of Dietary Supplements recommends a daily intake of vitamin D of 600 IU (15 mcg) for adults up to age 69 and 800 IU for adults 70 and older. The tolerable daily upper intake for vitamin D in adults is 4,000 IU (100 mcg).
Symptoms of vitamin D toxicity (a.k.a. hypervitaminosis d) can include a loss of appetite, weight loss, excessive urination, and heart arrhythmia. High doses of vitamin D can raise blood levels of calcium (hypercalcemia), which can damage the heart, kidneys, and blood vessels (NIH, n.d.). One example of the kidney damage hypervitaminosis D can cause is the formation of kidney stones.
- Vitamin D is a prohormone that stimulates several key body processes
- It may bolster the immune system, keep bones strong, and help protect against cancer.
- It is possible to get too much of a good thing.
- To prevent vitamin D toxicity, talk with a healthcare provider about how much vitamin D you should take.
Vitamin D toxicity is not very common. It results from taking too many vitamin D supplements. It’s not possible to overdose on vitamin D from the sun (the body self-regulates how much it takes in), and it’s very unlikely to do so via food (NIH, n.d.).
The NIH points out that symptoms of vitamin D toxicity are “unlikely” if you take less than 10,000 IU (250 mcg) daily, but that doesn’t mean you want to go that high. Some studies have shown that it’s possible to have too high a blood level of vitamin D, which is associated with a higher risk of death from any cause, cancer in areas like the pancreas, and a higher risk of heart disease (NIH, n.d.).
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What is vitamin D?
A bit of an impostor, for one. Vitamin D is technically a prohormone—not a vitamin—which means that it’s a substance that causes the body to create a hormone (which is simply something that spurs cells or body processes into action).
In the case of vitamin D, about 90% of what exists in the human body is produced in response to sun exposure on the skin, hence its nickname “the sunshine vitamin” (Mendes, 2018). (The remaining 10% comes from a variety of food sources, like fatty fish, milk, and egg yolks.) From there, the liver and kidneys turn vitamin D into various substances that can be used for key bodily processes, like immune system support, bone health, and cancer protection.
Much of the world’s population is deficient in vitamin D—up to 1 billion people worldwide, and 40% of Americans (Parva, 2018). Some researchers call it a “silent epidemic.” But that doesn’t mean you should go balls-out in adding vitamin D to your daily routine.
Vitamin D’s role in the body/benefits
Bone health/osteoporosis prevention
Vitamin D’s primary role is to help the body maintain the right levels of calcium and phosphorus. It affects how calcium is absorbed from food and how the body builds and reabsorbs bone (which the body is constantly doing; it’s a process called bone remodeling). Studies suggest vitamin D could help prevent fractures and osteoporosis (bone loss) (Bischoff-Ferrari, 2005).
A lack of vitamin D has been associated with an increased risk of infection and a higher chance of autoimmune diseases. It seems to bolster the body’s innate immune system, helping it destroy bacteria and other invading microbes (Aranow, 2011).
Protection from certain cancers
Some studies have found that vitamin D might have a protective effect against a number of cancers, particularly colorectal and breast (Meeker, 2016). A low vitamin D level is associated with a higher risk of those cancers.
That could be because vitamin D regulates the genes that control cell differentiation, division, and death. This helps control cell growth, bolsters the immune system, and reduces inflammation—all processes that can affect the development of cancer.
Regulates insulin, reduced risk of diabetes
Regular doses of vitamin D early in life have been found to reduce the risk of type 1 diabetes, and taking vitamin D later in life seems to reduce the risk of type 2 (Schwalfenberg, 2008). Vitamin D seems to help the body process insulin and control blood sugar.
One study found that vitamin D deficiency is associated with several risk factors for cardiovascular disease, including high blood pressure, coronary artery disease, cardiomyopathy (enlargement of the heart muscle), and diabetes. The study also found that vitamin D supplementation was associated with better survival (Vacek, 2012). However, other studies haven’t found those benefits (NIH, n.d.).